1. Field of the Invention
This invention relates to photographic products and, more particularly, to novel photographic film packs.
2. Description of the Prior Art
Photographic film packs or magazines adapted to house and dispense a plurality of diffusion transfer film units in stack rather than roll form are conventional and well known in the photographic art. See, for example, U.S. Pat. Nos. 3,080,805; 3,479,184; and other patents assigned to the present assignee.
One familiar film package of the type described takes the form of a generally flat, elongated container having an exposure opening in a forward wall through which light from the scene being photographed can be focused, and an exit opening in one transverse end through which a film unit can be withdrawn from the container subsequent to exposure for processing by the camera. Each film unit includes a negative and a positive element in the form of a pair of sheets, each of which has an appropriate photographic coating on one surface, e.g., a photosensitive coating and an image-receiving coating, respectively. The format is such that the sheets are stacked in superposed relationship with the coatings of each sheet facing in the direction of the exposure opening. A pressure plate is disposed between the stacks to urge the negative sheet into a plane that coincides with the focal plane of the camera into which the film package is inserted. Web means interconnect the sheets and are cooperable with the pressure plate so that the negative sheet can be longitudinally moved, after exposure, relative to the container until the negative sheet is positioned in registration and in superposition with the positive sheet, with the coated surface of each facing the other. In this condition, the sheets are in what is termed superposed face-to-face registration and the introduction of processing liquid between the sheets effects photographic development and the transfer of the image from one sheet to the other. Such introduction takes place when both sheets are longitudinally moved while in said superposed face-to-face registration through the exit opening of the container and between a pair of pressure-applying members such as juxtaposed rollers or platens mounted on the camera. The construction is such that initial movement of the sheets as a unit fractures a pod of the processing liquid attached to the film unit, and the liquid is spread between the sheets upon withdrawal of the film unit from the camera. The diffusion transfer process then takes place outside of the camera. To facilitate removal of the unit from the film package, the exit opening of the container is made large enough to effect free longitudinal movement of the positive and negative into and through the exit opening.
One problem encountered with film packs of the aforementioned type is that one may from time to time obtain varying amounts of a defect known as "white specks" across the picture area of the transfer print, which may detract from the quality of the photographic reproduction. This objectionable defect normally takes the form of minute white spots throughout the picture area.
It is the primary object of the present invention to provide an improved film pack of the type just described which does not suffer or suffers to a considerably lesser degree from the above-mentioned defect. That is to say, the present invention provides specific means for eliminating, or substantially reducing to an acceptable level, the number and severity of white specks in a picture obtained from such film packs.